Re: [Openvpn-users] OpenVPN tunnel stopped working (no traffic) after upgrade to OpenVPN 2.7 (Fedora 44)

Gert Doering <[email protected]> Mon, 18 May 2026 16:16:32 +0200

Newsgroups	gmane.network.openvpn.devel
Message-ID	<[email protected]>

Hi,

On Mon, May 18, 2026 at 03:58:33PM +0200, Piotr Dobrogost wrote:
> On Mon, May 18, 2026 at 9:22???AM Antonio Quartulli <[email protected]> wrote:
> > Piotr, not sure I asked before: could you check the stats with 'ip -s
> > link ovpn-sfx' ?
> 
> I will, but in the meantime, I wanted to ask a question: is dco on the
> server and client totally independent in the sense that it can be
> turned on only on one side and not on the other side, and it would
> work on the side where it's turned on?

If not, it would be a bug.  The intent is that the wire-format packet
"out on the network" does not any difference between a DCO-enabled and
a userland implementation.

(Also we test interop linux/linux+dco/freebsd/freebsd+dco/... and
this all works)

There are corner cases where features that are DCO-incompatible are not
detected properly, so things break if DCO is enabled - but we think we
have found them all (like, a server insisting on pushing compression
settings even if the client signals "I do not support compression", 
which is a situation that just happened to work with the userland windows
client...)

gert
-- 
"If was one thing all people took for granted, was conviction that if you 
 feed honest figures into a computer, honest figures come out. Never doubted 
 it myself till I met a computer with a sense of humor."
                             Robert A. Heinlein, The Moon is a Harsh Mistress

Gert Doering - Munich, Germany                             [email protected]

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